def findFalseCoin(coins, start, n):
    coins_list1 = []
    coins_list2 = []
    single_coin = []
    coins_list1_sum = 0
    coins_list2_sum = 0
    single_coin_value = 0

    if len(coins) == 1:
        return coins[0]

    if n % 2 == 0:
        for i in range(n):
            if i < n / 2:
                coins_list1.append(coins[i])
            elif i >= n / 2:
                coins_list2.append(coins[i])

        for item in coins_list1:
            coins_list1_sum += int(item)
        for item in coins_list2:
            coins_list2_sum += int(item)

        if coins_list1_sum > coins_list2_sum:
            return findFalseCoin(coins_list2, 0, len(coins_list2))
        elif coins_list1_sum < coins_list2_sum:
            return findFalseCoin(coins_list1, 0, len(coins_list1))
        elif coins_list1_sum == coins_list2_sum:
            return -1

    elif n % 2 != 0:
        for i in range(n - 1):
            if i < (n - 1) / 2:
                coins_list1.append(coins[i])
            elif i >= (n - 1) / 2:
                coins_list2.append(coins[i])
        single_coin.append(coins[n - 1])

        single_coin_value = int(single_coin[0])
        for item in coins_list1:
            coins_list1_sum += int(item)
        for item in coins_list2:
            coins_list2_sum += int(item)

        if coins_list1_sum == coins_list2_sum:
            if coins_list1_sum == single_coin_value:
                return -1
            elif coins_list2_sum < single_coin_value:
                return findFalseCoin(coins_list2, 0, len(coins_list2))
            elif coins_list1_sum > single_coin_value:
                return single_coin[0]
        elif coins_list1_sum > coins_list2_sum:
            return findFalseCoin(coins_list2, 0, len(coins_list2))
        elif coins_list1_sum < coins_list2_sum:
            return findFalseCoin(coins_list1, 0, len(coins_list1))


if __name__ == "__main__":
    usr_input = input("")
    original_coins_list = usr_input.split(",")
    coins_list = original_coins_list

    fade_coin = findFalseCoin(coins_list, 0, len(coins_list))
    if fade_coin == -1:
        print("Fake coin is not found")
    else:
        for index, value in enumerate(original_coins_list):
            if fade_coin == value:
                print(f"Fake coin:{index}")
